Detect window closing event in AIR application

How do I detect the window closing event in an AIR app? Tried the following.

deactivate and windowDeactivate events in the WindowedApplication tag.
addEventListener(Event.CLOSING, onClose);
addEventListener(AIREvent.APPLICATION_DEACTIVATE onClose);
addEventListener(AIREvent.WINDOW_DEACTIVATE, onClose);

None of them seem to work.
Any ideas?

Thanks
CS